Gaviscon vs Rennie and other heartburn remedies

Heartburn might not be on your Christmas wish list, but it may make an uninvited appearance thanks to some festive overindulgence. 

We asked Alwyn Fortune, community pharmacist and policy lead for the Royal Pharmaceutical Society, to tell us what you can do to prevent and treat digestive discomfort this Christmas.

Plus, we compare the available remedies on cost and active ingredients to help you choose the best option for you.

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Heartburn remedies compared

Over‑the‑counter heartburn remedies such as Rennie and Gaviscon typically work by:

• Neutralising excess stomach acid, using antacids such as calcium carbonate or sodium bicarbonate. 
• Forming a protective barrier over the stomach contents to help stop acid rising into the oesophagus (using alginates such as sodium alginate). 

Usually taken after a meal or at the onset of symptoms and can come in liquid or tablet form.

The major brands (Rennie and Gaviscon) can be pricey, and there are lots of variants to choose from. Here we explain how to pick the right one for you:

What's the difference between Gaviscon Original, Advance and Double Action?

All three main products in the Gaviscon range contain a combination of alginates and antacids as their active ingredients, and come in liquid and tablet form.

The key difference is the amount of active ingredients they contain. 

Gaviscon Original is the standard, lowest-strength formula, liquid contains 500mg sodium alginate per 10ml.

Gaviscon Advance has a higher concentration of sodium alginate than Gaviscon Original — 1,000mg per 10ml in liquid form and 500mg per tablet.

Gaviscon Double Action contains more acid‑neutralising calcium carbonate (325mg per 10ml and 187.5mg per tablet) than Gaviscon Original.

If you need to watch your sodium intake, Gaviscon Advance Peppermint and other Advance versions often have a lower sodium content per dose than many other products in the Gaviscon range, but check the flavour and label for the exact amount.

There are several flavours of each, including mint, aniseed and mixed berries. Check the label to ensure it's suitable for your stomach and dietary requirements.

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Cheapest place to buy Gaviscon

When we looked at prices for a 500ml bottle of Gaviscon Original liquid on 15 December 2025, among the cheapest were:

• Savers (£9.99 for 500ml, £1.99 per 100ml)
• Instant Pharmacy (£10.99 for 500ml, £2.19 per 100ml)

It typically costs £13-14, but there are periodic offers on at supermarkets and high street pharmacies, so it's worth shopping around. You should be able to find it for between £10 and £12.

Gaviscon Advance and Double Action are generally more expensive – with a retail price of £16.99 in Superdrug for a 500ml bottle of Gaviscon Double Action, £10.99 for a smaller 250ml bottle and £6.39 for an even smaller 150ml bottle.

However, again, it's worth looking out for multi-buys or loyalty card offers in supermarkets and high street pharmacies. 

There are also own-brand or generic alternatives, including:

• Peptac antacid solution, £7.49 for 500ml (£1.50 per 100ml), available at Pharmacy2U
• Acidex Liquid oral suspension, £5.99 for 500ml (£1.20 per 100ml), available at Savers
• Tesco Heartburn and Indigestion liquid, £6.20 for 500ml (£1.24 per 100ml), available at Tesco
• Superdrug Indigestion and Heartburn Relief, £6.99 for 500ml (£1.40 per 100ml), available at Superdrug
• Sainsbury's Heartburn and Indigestion liquid, £6.20 for 500ml (£1.24 per 100ml), available at Sainsbury's
• Boots Heartburn Relief, £6.90 for 500ml (£1.38 per 100ml), available at Boots

How to save money on Gaviscon

Buy larger quantities or volumes

Smaller bottles are typically worse value, although if you don't need to take Gaviscon regularly then you may not need a big bottle. Once opened, Gaviscon liquid should be used within six months, provided it is stored below 30°C and not refrigerated or frozen, and the expiry date on the bottle has not passed. 

Bottles are generally cheaper than tablets or sachets

Liquid sachets are typically pricier per dose, although if you are travelling, you may find these or tablets more convenient than a heavy glass bottle. 

Tablets can cost more, but it depends on the offer you find. Bear in mind when comparing the cost that you're usually recommended to take two tablets, and a dose of the liquid is 10-20ml for adults.

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Rennie and other antacids compared

Other over-the-counter heartburn remedies include antacids, which just contain an acid neutraliser.

They typically contain calcium carbonate or other antacid salts such as sodium bicarbonate as the active ingredient. Formulas with sodium bicarbonate should be avoided if you're on a low-salt diet.

Antacid tablets are typically cheaper. For example, we found Rennie indigestion tablets for 16p per two-tablet dose (£5.99 for 72 tablets, Superdrug), and own-brand versions for around 12p per dose. The cheapest Gaviscon liquid we found, by contrast, was around 30p per dose.

These all contain slightly less calcium carbonate — 500mg per tablet rather than the 680mg in Rennie:

• Setlers antacid chewable tablets, £1.49 for 24 (6p each), available at Savers 
• Superdrug antacid tablets, £2.99 for 48 (6p each), available at Superdrug
• Boots indigestion tablets £3.30 for 48 (7p each), available at Boots

Most are chewable, so you may find them convenient when on the go.

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Longer-acting options: proton pump inhibitors and H2 antagonists 

Longer-acting or preventative acid reflux treatments include proton pump inhibitors (PPIs), such as omeprazole and esomeprazole, and H2 antagonists. Both work to reduce the amount of acid your stomach produces.

Omeprazole - can you get it without a prescription?

In the UK, Omeprazole is available both over the counter (OTC) and on prescription.

OTC: Lower-dose Omeprazole (usually 10 mg or 20 mg) can be bought from pharmacies for short-term relief of heartburn or acid reflux, generally only recommended to use for up to 2 weeks.

Prescription: Higher doses or longer-term treatment for conditions such as stomach ulcers, severe reflux or other medical conditions require a GP prescription.

If you have more persistent issues, your doctor or pharmacist may recommend one of these medications. It's always a good idea to discuss with a health professional before taking anything, as there are potential side effects of Omeprazole that you need to weigh up, and it's important to rule out any other health issues first.

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Home remedies for heartburn and acid reflux

Heartburn can strike suddenly, so you may not always have remedies to hand. Alwyn Fortune suggests these home measures:

• Loosen your clothing. Tight clothing such as a waistband or belt can place pressure on the stomach.
• Sip baking soda with water. Also known as sodium bicarbonate, add half a teaspoon to half a cup of water and drink this alkaline solution to neutralise stomach acid. Choose baking soda or bicarbonate of soda, not baking powder, which also contains an added acid, so it is not the same. This is not suitable for regular use or for people with high blood pressure. 
• Drink fat-free skimmed milk. This can bring relief by acting as a temporary buffer between the lining of the stomach and its acidic contents. 
• Elevate the head of your bed. The NHS recommends using wood, bricks or books to raise the head of your bed by around 10-20cm so your chest and head are above your waist. This can help to stop stomach acid travelling towards your throat when you're sleeping. Don't use additional pillows, as this can increase pressure on your stomach and even worsen symptoms. If it's a regular problem you may want to consider an adjustable bed.

However, Alwyn warns: 'While these actions may offer temporary relief, persistent symptoms warrant medical attention for a proper diagnosis and treatment.'

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How to prevent heartburn

Lifestyle and diet changes can help to manage symptoms:

• Eat smaller meals. Small, frequent meals are better than big ones, and it can be worth avoiding trigger foods. The NHS offers advice on heartburn and acid reflux and claims the conditions are sometimes made worse by coffee, alcohol, chocolate, tomatoes and fatty or spicy foods.
• Don't eat near to bedtime. Leave three or four hours between eating and going to bed so your food has time to settle.
• Adopt a healthy lifestyle. Being overweight or being a smoker can cause or worsen heartburn, as can some medications such as anti-inflammatories (the likes of ibuprofen).
• Manage anxiety and stress levels. Studies have suggested that anxiety or depression may increase the risk of acid reflux.

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When to see your doctor about acid reflux or heartburn

Heartburn and acid reflux are common conditions, especially in adults aged 40 and above, but if you're not getting relief from over-the-counter treatments, or it's a new or persistent issue, it's worth seeing your doctor.

A stomach ulcer, hiatus hernia (where part of your stomach moves up into your chest) or a bacterial infection may be responsible for your symptoms, or it may be gastro-oesophageal reflux disease (GORD) and require investigation or treatment.

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